Manufacture of ferrocobalt



9 v F. L. BOSQUI f 2,058,12

.MANUFACTURE OF FERROQOBALT I Filed June 29, 1953 aren TO R Patented Oct. 20, 1 936 MANUFACTURE oRFnartoooBALr Francis Lawrence Bosqui, NK na, Northern:

Rhodesia,

assignor toi Rhokana Corporation Limited, NKana, Northerrr'Rhodesia I Application June 29, 1933, SerialpNo. 678,300

"1 Claim. (01, cor-.57)

The present invention refers to the electrolytic production of ferro-cobalt.

According to the invention ferro-cobalt is obtained by electro-deposition from a solutionof iron and cobalt which is maintained substantially neutral, but on the acid side of actual neutrality in order to ensure that the iron and cobalt appear at the kathode as metals and not as hydrates, as would be the case if the solution should become basic. The free acid present should be below three grams per litre reckoned as sulphuric acid, and is conveniently maintained at from one to twograms per litre in order to keep the acidity of the solution under control.

The invention further relates to the electrolytic production of ferro-cobalt from material containing iron, cobalt and another metal such as copper ora metal lower than copper in the electrochemical series, which requires to be excluded from the ferro-cobalt and which may itself be a valuable productt In this respect the invention comprises the treatment of the raw material to form a solution of iron :and cobalt containingas-impurity so much of the copper or other metal above referred to as technical or economic considerations necessitate entering the solution. The solution is then subjected to a purifying step to eliminate such impurity metal or to reduce it to a degree which is not detrimental.

The purified solution is continuously supplied as katholyte to an electrolytic cell in which ions from the anode are excluded from the neighbourhood of the kathode. For this purpose there may be employed the known form of cell in which the kathode element and the anode element are separated by a partition sufficiently porous for electrolyte to flow through it and the katholyte is caused to flow through the partition from the 40 kathode compartment to the anode compartment at a rate sufiicient to prevent the migration or diffusion of anode ions into the kathode compartment. The solution thus introduced into the kathode compartment is maintained in the state of acidity mentioned above; and under these conditions ferro-cobalt of substantial purity is deposited at the kathode.

The solution which is thus to be purified and electrolyzed may be obtained for instance by leaching an ore or ore product. In such a case insoluble anodes are provided in the electrolytic cell and the acid anolyte displaced from the cell by the incoming katholyte is returned to the leaching plant. Where, however, the raw material contains the metals in a metallic state, it is preferred to employ. such .raw materials as the anode element. in the electrolytic cell, so that dissolution of the rawumetal and deposition of the ferro-cobalt goon simultaneously in the same cell. Theefiiuent ofthe cell in this case is neutral and is subjected to the purification step dur- By means of this procesolution is minimized, owing to the fact that much ofxthe copper is deposited directly in-the cell as sludge.

' The invention is illustrated in the accompanying diagrammatic drawing in which Figure 1' refers to the method in which dissolution of the raw =meta'l and-electro-deposition of the ferrocobalt are efie'cted in the same cell. Figure II illustrates-the procedure in which dissolution is effected outside the electro-deposition cell by anodic dissolution and by leaching respectively.

Referringto Figure I, 2 indicates an electrolytic' cell'coritaining cast anodes 3. Said anodes maybe analloy or mixture of metals obtainedby the reduction of slag which is produced in the smelting of a copper ore containing iron and notable quantities of cobalt.

The kathodes 4 may be of various materials such as rolled cobalt, iron, copper or stainless steel. The anodes and kathodes are separated by partitioning 5 which is sufiiciently porous to permit electrolyte to how through it; and a hydraulic head is maintained in the kathode compartments sufficient to cause flow of katholyte into the anode compartments at a rate equal to about litre per square foot of filter surface per hour. Flow at this rate substantially prevents access of ions from the anodes to the katholyte. 6 indicates a system for circulating the katholyte with the object of keeping its composition uniform and of assisting deposition. 7

Purified iron-cobalt sulphate solution is continuously fed to the kathode compartments from the storage tank I. A corresponding quantity of anolyte is continuously displaced from the cell at 8 and is conducted to purification apparatus 9. In the said apparatus it is treated for removal of its copper content; and the purified solution is returned by the pipe It to the storage tank I.

The acid radical liberated in the kathode compartment is carried through the partition 5 by the flowing electrolyte and causes the corrosion of the anodes 3. A low current density is desirable in order to limit the tendency of the ions liberated at the anodes to migrate or diifuse into the katholyte; a current density of about 10 amperes per square foot having been found appropriate.

Under these conditions the anodes 3 are corroded; their iron and cobalt content passing into solution. Some copper also goes into solution, the remainder depositing in the cell as anode sludge l I. By reason of the hydraulic head in the kathode compartments the solution thus produced flows out of the cell at 8 and is subject to treatment in the apparatus 9. In said apparatus it is so treated as to remove copper. It may for this purpose percolate through metal on to which the copper will cement, such for instance as iron or cobalt. It is desirable that the copper content of the purified solution should not exceed 0.05 gram per litre.

The solution going to the storage tank I is substantially neutral. It is there given a small addition of acid such that in the cathode compartments it will be substantially neutral but definitely not basic. It is found desirable to have about one to two grams per litre of free acidreckoned as sulphuric acidpresent in order to ensure that the solution will not become basic around the kathodes, which would result in iron and cobalt hydrates apppearing at the kathode. The solution thus slightly acidified passes from the storage tank I to the kathode compartments; and being there protected against contamination by positive ions from the anode compartments, it deposits substantially pure ferro-cobalt on the kathode plates.

In Figure II there is shown the same electrolytic cell 2 comprising kathodes 4, porous partitioning 5, an inlet for purified katholyte from the storage tank 1, and the outlet 8. In this case, however, the anode 3a. is insoluble so that the liquid discharged from the cell at 8 is acid. This acid liquor is used for dissolving the raw material.

In Figure II it is shown as being passed for this purpose through the electrolytic cell l2 comprising anodes |3 composed of raw metal which may be of the same composition as the anodes 3. The kathodes I 4 are required to act merely as conductors of electricity and may be copper plates. Acid is added at l5 to maintain the electrolyte in this cell at an acidity exceeding three grams per litre of free acid reckoned as sulphuric acid. Under these conditions the iron and cobalt content of the anodes l3 goes into solution.

Some of the copper content of said anodes plates on the kathodes l4 and some falls to the bottom of the cell as sludge. Some quantity of copper goes into solution and so passes to the purification tank 9 where it is removed from the solution. The purified iron and cobalt solution is conveyed to the storage tank I and fed as katholyte to the cell 2, where, as in the previously described example, the katholyte is substantially neutral and where accordingly ferro-cobalt is deposited on the kathodes.

The ferro-cobalt kathode deposit is washed and dried then melted and cast into marketable shapes. The copper is suitably dealt with, as by smelting and casting into commercial shapes.

I claim:

The process which comprises the steps of anodically dissolving anode material containing cobalt, copper and iron alloy in an electrolyte the acidity of which is from three to five grams per litre, thereby preventing deposition of the cobalt and iron, withdrawing electrolyte containing cobalt and iron from the cell, removing the last traces of copper obtained therein, supplying the thus purified liquid as catholyte in another cell in which electrolysis is so conducted as to exclude anode ions from the neighbourhood of the cathode, in which other cell the anode is insoluble and in which the acidity of the electrolyte is maintained at 1-2 grams per litre of free acid, thereby cathodically depositing cobalt iron alloy from the catholyte, regenerating acid at the anode, and supplying acidified electrolyte to the dissolving cell.

FRANCIS LAWRENCE BOSQUI. 

